不能使用await我的UserManager实例(Cannot use await with my instance of UserManager)

 我正在尝试使用UserManager的实例提取所选用户，以便在视图中显示有关特定用户的详细信息。 我想使用以下代码行： 
 
var user = await _userManager.Users.SingleOrDefaultAsync(m => m.Id == id);
 
 但是，这会产生以下错误： 
 
 “'await'运算符只能在异步方法中使用。” 
 
 我真的很困惑，因为SingleOrDefaultAsync方法肯定是一个异步方法 - 线索就在名字中！ 当我将鼠标悬停在鼠标上时，它甚至会说'等待'，那么为什么我不能在这种情况下使用'await'关键字呢？ 
 
 我已经尝试取出'await'关键字，然后它会编译，但如果我尝试访问View，我会收到以下错误： 
 
 InvalidOperationException：传递给ViewDataDictionary的模型项的类型为'System.Threading.Tasks.Task`1 [MyProject.Models.ApplicationUser]'，但此ViewDataDictionary实例需要类型为“MyProject.Models.ApplicationUser”的模型项。 
 
 对于上下文，这是我的控制器方法： 
 
    //
    // GET /Account/Details/5
    public IActionResult Details(string id)
    {
        if (id == null)
        {
            return NotFound();
        }

        var user = _userManager.Users.SingleOrDefaultAsync(m => m.Id == id);

        if (user == null)
        {
            return NotFound();
        }

        return View(user);
    }
 
 这是我的观点所期待的： 
 
@model ApplicationUser
 
 任何帮助都非常感谢，并且如果这是一件非常容易让我苦苦挣扎的事情而道歉，我仍然是.Net和MVC的初学者！ 

I am trying to extract the selected user using an instance of UserManager, in order to display details about a particular user in a view. I am trying to use the following line of code:
 
var user = await _userManager.Users.SingleOrDefaultAsync(m => m.Id == id);
 
However, this gives the following error:
 
"The 'await' operator can only be used within an async method."
 
I'm really confused, because surely the SingleOrDefaultAsync method is an async method - the clue is in the name! It even says 'awaitable' when I hover my mouse over it, so why can't I use the 'await' keyword in this situation?
 
I've tried just taking out the 'await' keyword, and it will then compile but if I try to access the View, I get the following error:
 
InvalidOperationException: The model item passed into the ViewDataDictionary is of type 'System.Threading.Tasks.Task`1[MyProject.Models.ApplicationUser]', but this ViewDataDictionary instance requires a model item of type 'MyProject.Models.ApplicationUser'.
 
For context, here is my controller method:
 
    //
    // GET /Account/Details/5
    public IActionResult Details(string id)
    {
        if (id == null)
        {
            return NotFound();
        }

        var user = _userManager.Users.SingleOrDefaultAsync(m => m.Id == id);

        if (user == null)
        {
            return NotFound();
        }

        return View(user);
    }
 
and here is what my View is expecting:
 
@model ApplicationUser
 
Any help is much appreciated, and apologies if this is a very easy thing that I'm struggling on, I'm still very much a beginner with .Net and MVC!

原文：https://stackoverflow.com/questions/46717039